I'm trying to simulate an ISP connected to a router, and the router is connected to a PC. I don't really know what to do on packet tracer, whether to connect a modem to the router and then connect the modem to the cloud or just connect the cloud to the router. and after connecting the router to the cloud, how to configure the cloud? I can't give it an ip or anything.and on GNS3 I really don't know what to do....

Thats a simple setup martin,here i m using public ips which i have ...here the issue is i configured the router interface in the same subnet and i tried pinging between these to and my switch also but i coudn't ping the internet from the router

i checked with my pc i can ping the internet from command prompt of my pc ....

i deactivated firewall in my pc but its not working...the question if can able to ping from pc then i should be able to ping from router also right but why its not working...

and also i observed some duplex mismatch message but i dont think that it is preventing that one

Sorry for the delay in responding. Loopback interfaces are always up, so you can create these to simulate "real" networks.

Martin, is correct. With GNS3 you can actually connect real equipment to the PC running GNS3 and therefore connect a "real" ISP as well as simulate one. Cisco PT can not do this, you can only simulate a real ISP.

Just watchout if using private IP on the GNS3 network, make sure you have a NAT device as Martin mentioned. He is using his Linksys for this, as am I at my home. Martin has a lot of GNS3 labs under his profile so be sure to check them out. Good stuff!!

So are you trying to "simulate" an ISP or are you trying to connect your GNS3 network to your home network and the "real" Internet? You mentioned "simulate" in one of your earlier posts.

You mention you are using public IPs. Have these been assigned to you? As Martin said, ping is a two-way street. Do you have a path back to you from the Internet? Do ping tests from your GNS3 network to your real LAN. Then to the real GW. Find out where the pings fail. and you will find the device that is the cause of the problem.

If you can post a topology of the GNS3 network and how it connects to your real network and the ISP connection, I am sure we could help you out.